1. Field of the Invention
This invention relates to 6-iodoethylated starch and a process for preparing the same. More particularly, it is concerned with 6-iodoethylated starch in which one iodine is attached per 5 glucose units and a process for preparing the same.
The 6-iodoethylated starch in the present invention is a novel compound which has not been disclosed in any literature. It is useful as a contrast agent for X-ray examination, especially for opacifying the vascular and lymphatic vessels.
2. Description of Prior Arts
As instruments for the radiographic diagnosis were diffused and diagnostic methods including computer tomography (CT) were developed in recent years, use of contrast agents for diagnosis has been much increased in therapeutic practice.
Contrast agents for the vascular vessels currently widely used are those which comprise an iodine compound of benzoic acid as the opacifying component. Whereas these contrast agents are highly capable of opacifying the vessels under X-ray examination, they cause pain or feeling of heat in patients on introduction into the blood vessel. In addition, they are apt to cause allergic reactions of various degrees, and occasionally death due to severe anaphylactic reactions are reported.
On the other hand, the lymphatic vessel-contrast agent primarily used is the ethyl ester of poppy oil-fatty acids. The contrast agent, which comprises oily iodine compounds, is not leaked through the wall of the lymphatic vessels to reach the desired site and causes the vessels to cast distinct densities. However, since composition of the agent is oily, it may cause embolization of the peripheral blood vessels when passed from the lymphatic system to the vascular system. It is known that there are caused pulmonary embolisms frequently as well as severe adverse reactions such as cerebral infarction.
In view of the difficulties discussed above, development of safer and superior contrast agents has been desired.